Side-chain chlorination of benzene derivatives



@et 27, i931.

E. E. CONKLIN SIDE CHAIN CHLORINATION OF BENZENE DERIVATIVES Filed Dec.26, 1923v /lar Tau/a1.

WITNESS Arrofmfys cient and continuous rocedure.

Patented @et 27, 193i massa 'il' Il' CONKIIN, 0F SYRC'USE, NEW YORK,ASSIGNOR, .BY .'BIIIFSNE ASSIGN- Mml'l', E@ THE SOLVY PROCESS COMP, 0FSOLVAY, NEW YORK, A CORPORA- TION" 0F N YORK tomamos or emanan Dnarvarsapplication. mea December as, icas. serial no. esame.

This invention relates to the side-chain chlorination of benzenederivatives such as toluol and the particular object of the invention isto produce benzyl' chloride by an efli- Heretofore, as out ed in thepatent of Gibbs-and Geiger, No. 1,246,739 of November 13, 1917, the thenprevailing methods for the production of side-chain chlorinesubstitution products of toluol (benzyl and benzal chloride andbenzotrichloride) consisted either (a) of batch or intermittentprocesses in which a given amount of toluol was treated 1n liquid formwith chlorine gas until thr reaction had' roceeded to a predeterminedpoint or o? processes in which toluol as gas was introduced intosuitable apparatus in which it came in contact with gaseous chlorine. Inthe former or batch process, after the reaction had reached apredetermined' point, the char e was removed and treated for theisolation o the desired roduct in a more or less pure condition. Lightor heat or a catalyst, alone or in combination, were used to favor thereaction. An example of a speciiic process operating along these linesis `ven in Patent No. 1,345,373 to Kyrides, iily 6, 1920. Processes ofthis character have the disadvantage of Huctuating conditions andrelatively large apparatus. Large apparatus is in this case a particulardisadvantage on account of the highly inflammable nature of toluol andthe necessity of using glass in order to obtain the advantage oflillumination either by sunlight or some artificial source of light.

In the other ty of process, in which toluol is chlorinated w ile ingaseous form, it was1 necessary to employ a temperature above that ofthe boiling point of toluol (111 C.) and 1n. the reaction productunattacked toluol, which was usually considerable in amount, required tobe separated and returned to the system for further treatment. Light ora catalyst or both were employed as accelerating agents.

, Patent No. 1,202,040, C. Ellis, October 24,

1916, describes such a-.process and the patent to Gibbs and Geiger lirstreferred to, No. 1,246# 39, is for a modification of this second type ofprocess and for the use of ultraviolet rays as the acceleratingagenttherein. Processes of .this character ave the-disadvanta of working withan inflammable material 1n vapor form'and are confronted with thedifculty of maintaining lar e apparatus at an elevated temperature an aconstant tempzrature such that condensation does not take p ace.

The process of this invention, in contredistinction to the processes ofthe prior art, is

one in which the reaction proceeds continu' ously and in the liquidphase. Uniform conditions are obtained and the output fromJ a unitinstallation is relativelyv lar e. Other advantages will be evident fromt e'detailed' description.

Apparatus suitable for the practice of the new process is indicated inthe accompanying drawings in which Fig. 1 is a side ele- .vation oftheapparatus, Fig. 2 is an enlarged sectional view of a detail and Fig. 3is a horizontal section on line 3-3 of Fig. 2.

In the drawings A is a tower constructed of sections B of glass filledwith-suitable packing C such `as glass Raschig rings. The glass sectionsare constituted of a material of the type known in the market as Pyrexglass, a transparent vitreous material which is not destroyed byexposure to heat. Each of the glass sections B loit the tower A isapproximately 6 inches in diameter and approximately t feet in length. Asuitable cement D, resistant to chlorine and the other reactionsubstances may be used in the connection v various pipe connectionshereinafter referred to, although for the glass sections it ispreferable to employ packing means like those shown in Figs. 2 and 3.Toluol, preferably hot and in regulated amount, is continuouslyintroduced into the top of the tower at E and dry, pure chlorine gas atF at the bottom of the tower. If sunlight is not available, artificialillumination, such as that from electric or mercury lamps, may be usedby placing lamps G at regular intervals around the tower A. Thechlorinated and finished roduct is continuously withdrawn throu theyline H. The hydrochloric acid gas, w ich is producedby thereactionbetween the toluol and the chlorine escapes throu h the line I andleaves the system through t e line J and may be utilized by absorptionin water with the production of muriatic acid or in any other suitablemanner. Any toluol entrained or carried away as vapor in the gas leavingthe tower through the line I, is condensed in the cooler K and returnedto the tower A at L. The tower A may be conveniently supported asindicated in Figs. 2 and 3 from suitable uprights P with cleats orshelves Q secured thereto at regular intervals. On

Y these cleats Q. rest boards S each centrally apertured to supportoneof the glass sections B, preferably on a cushioning ring R. The

annular s ace between adjacent sections B may be lled with, cork rings Tsuitably treated, as by soaking in glue, said cork rings beingsurmou'nted by a lead follower 'ring U upon which rests a second late Sysimilar to S in Shape and positioned y the bolts V and nuts W. The boltV passes loosely through S so that any desired tightening of the nuts Wmay be eiiected. The construction is preferably such that the lower edgeof each section B remains out of contact with the upper portion of thenext lower section B.

The process as thus described consists essentially in passing a streamof toluol as a liquid at a suitable temperature in countercurrent flowand in intimate contact with a current of chlorine gas, downwardlythrough a tower transparent to light and which is subjected to sunlightor artificial illumination. With suitable regulation of the temperatureand of the amount of toluol introduced through E and of the chlorineintroduced through F the reaction proceeds rapidly and no recirculationof the exit liquor from H a-nd no cooling or heating of the tower isrequired in order to obtain the desired chlorination. Furt-hermore,practically complete utilization of the chlorine takes place so thatvery little, if any, chlorine escapes at J. Another result is thatpractically no chlorination in the benzene ring occurs with theproduction of ring chlorinated toluol derivatives ("chlor toluols) whichimpurities are dilicult to remove. rIhus an analysis of a crude benzylchloride product made in accordance with the new process and having aspeciic gravity of 1.048 showed only a fraction of one percent. of ringchlorine and over siX'een percent. side-chain chlorine. Thatcorrespon-ds to a benzyl chloride content of over titty-seven percent.It should, however, be stated that the product to which the foregoinganalysis applies was a product oic the process as carried out in itsearly stages and that stili more favorable analysis may be developed asthe process is practiced' on commercial scale.

For the production oi benzyl chloride satisfactory results are obtainedwhen the tower A is approximately 32 feet high and is illuminated everyi feet with two 200 watt electric lamps. A suitable temperature for thetoluol introduced at E is 80 to 100 C. At the lower temperature theliquor returned through L is very small. When the operation is firststarted, the ilow of toluol at E is less than normal and the flow isgradually increased during about the first hour while the requiredtemperature and other chlorinationy conditions are becoming establishedthroughout the tower. The operation then proceeds `practicallyautomatically with a. substantially, constant and continuousintroduction of toluol at E and a corresponding constant and continuouswithdrawal of crude product of the desired gravity at H. The capacity ofthe apparatus described is about 1800 lbs. of crude benzyl chlorideproduct in twenty-four hours. The toluol may be conveniently supplieddirectly from a toluol still, the condenser of which is so adjusted asto cool the condensate to only 80 to 100 C. and with a small receiver ortrap' for the condensate provided with a constant level over-flow sothat the loW through E is independent of the fluctuations in operationof the still.v

The various gas and 1i uor lines E, F, I-I, I, L K and J are'preferablymade of glass or of lead.

The crude products 'from H may be treated in a variety of ways for theisolation of the chlorine derivative depending on the purity desired.For example, it may be first washed with a suitable alkali such assodium carbonate solution until it no longer reacts acid, whereupon itis fractionally distilled in vacuo.

The process has been described with particular reference to theproduction of benzyl chloride but with pro er adjustments it should besuitable for urther chlorination of toluol to produce benzal chlorideand benzotrichloride and for the production of side-chain chlorinesubstitution products of other side-chain aromatic hydrocarbons besidestoluol. v

The invention thus contemplates the treatment not only of toluol but ofits homologues and when in the claims the phrase hydrocarbon of the typeof toluol is used, it is intended to refer to toluol or any homologousside-chain aromatic hydrocarbon.

It will be `apparent that a glass tower feet or so in height and 6inches or so in diameter and composed of a multiplicity of tubular glassunits is a tower which is not self-supporting but requires support fromthe eirterior. In this art the use orn a glass tower of this type is, soitar as the applicant is aware, entirely novel. @ther inatcriai thanglass may be used in the construction of such a tower provided itpossesses the qualities of transparency, durability and resistance tothe chemicals to which'it is exposed and the temperatures involved.Where the lil tenesse eective light rays are referred to, they areintended to include all those rays or emanations ywhich favorhalogenation whether such rays are luminous or invisible.

Numerous modifications in the detail of construction and operation mayobviously be employed without departing from the spirit of thisinvention.

l claim:

l. In the art of chlorinating a hydrocarbon of the type of toluol, theprocess which consists in exposing a flowing stream of the material tobe chlorinated to an oppositely flowing stream of chlorine'gas andsimultaneously feeding the stream of materia-l ,to be chlorinated pastazone of effective light rays and maintaining the material durmg thistreatment in a condition of liquidity and intimate contact with thechlorine gas while the gaseous chlorine and liquid hydrocarbon are inreactive relation with each other.

2. The process which comprises establishing and maintainingv a regulatedflow of a hot hydrocarbon of the type of toluol into a reaction chamberof a predetermined length, causing the same to dow in a downwarddirection thru said chamber past a zone of eective light rays in astateof continuous li uidity and intimate contact withV a regu atedcounter-current :dow of chlorine gas, and withdrawing from the reactionchamber the product formed, whereby the product will continuouslypossess an approxlmately constant predetermined specilic gravity.

3. in the art of chlorinatingtoluohtheprocess which comprises passing aheated liquid stream of the hydrocarbon to be chlorinated intocontact'with an oppositely flowing stream orn chlorine and exposing the streamsas they flow in opposite directions in Contact with each other toeffective light rays, collecting` the resulting chloride, subjecting theresulting hydrochloric acid gas and the vaporized portion o thehydrocarbon to condensation, returning the condensed hydrocarbon to 6.ln the art of chlorinating a hydrocarbon.

of the type of toluol, the process which comprises passing a heatedliquid stream of the hydrocarbon to be chlorinated thru a conduittransparent to light, passing a stream of chlorine gas thru said conduitin intimatecontact with and in counter-current iiow to said stream ofhydrocarbon, and exposing the streams as they liow in oppositedirections to eEect-ive light rays.

ln testimony whereoe I have hereunto set my hand,

E. BIDDLE CONKLN.

the hydrocarbon stream, and removing the hydrochloric'acidgas.

4. ln the art of chlorinating a hydrocarbon ot the type of toluol, theprocess which comprises estahlishing a continuous dow in a state of linedivision of heated liquid constituted of the hydrocarbon to bechlorinated and si multaneously edecting contact between said :flowingliquid and chlorine gas continuously' lowing in an opposite direction,exposing the two reagents as they iiow in opposite directions in Contactwith each other, to effective onnrrrienrn or ooRRncTroN,

mem No. rendere. ommen october 27, 1931, to

.EARL MHLE GNKLLIN,

it is hereby certified that error appears in the printed specificationof the above numbered: potent requiring correction as follows: ?age 2;line 95, for "products" read product; page 3,l line 35, clairn'3, after"chlorinating" insert n hydrocarbon oi .the type amend that the saidLetters Patent should be readl with these corrections therein that thesame may conform Ato the Vrecord of the cene in tire Potent Uiiice.. l

Signed and sealed this 22nd doy of December, A, D. 1931.

M. I. Moore.

(Seal) Acting Commissioner of Patents.

